Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide

Definitions

• This invention relates generally to refractories of high alumina content, generally in the range of from about 85 to about 95%, of alumina, the balance being essentially silica, with minor amounts of impurities such as TiO Fe O alkalies and alkaline earths normally associated with the alumina and silica.
• These bricks are generally manufactured from high purity, high density A1 0 grog material and a siliceous binder.
• Traditional forms of silica used for this purpose are various kinds of clays, usually kaolin or ball clay, and ground silica sand.
• the present invention is based upon the discovery that the addition, to the alumina-silica brick batch mix, of a small amount of a lithium compound, as hereinafter discussed more in detail, plus a small amount of at least one of an alkaline earth metal compound and an iron compound, as discussed more in detail hereinafter, increases the cold strength of the resulting burned brick while at the same time decreasing its reheat expansion and its apparent porosity without deleteriously affecting its refractoriness under load. In fact, improvement in the refractoriness under load has been realized through the addition of the stated combination or compounds.
• the present invention involves, in a high alumina refractory brick match mix consisting essentially of from about to about by weight, of alumina and from about 5 to about 15%, by weight, of silica, said percentages being based on the combined weight of said alumina and said silica, the improvement comprising: in addition, as added materials, of between 0.05 and 0.2% of at least one lithium compound selected from the group consisting of lithium fluoride and lithium carbonate and from about 0.01 to 0.3% of at least one other compound selected from the group consisting of calcium hydroxide, magnesium hydroxide and iron oxide, said amounts of lithium compound and other compound being by Weight based on parts of combined alumina and silica.
• the alumina grog employed in preparing the brick batch mix may be sintered or tabular alumina, fused alumina, calcined alumina, and the like.
• the alumina employed will contain at least 99% A1 0 preferably at least 99.5% A1 0
• a portion of the alumina will be relatively coarse particles, and a portion will be relatively time.
• from about 50 to about 65%, by weight, of the alumina will be 6+48 mesh (Tyler) and the balance (from about 35 to about 50%, by weight) will be 48 mesh.
• Preferably 'at least about 10%, say from about 10 to about 30%, by weight, of the alumina will be -325 mesh.
• the silica component will generally also be of high purity material containing at least 99% SiO preferably over 99.5% Si0 and especially about 99.9% SiO
• ground glass sand is particularly suitable.
• the silica will generally all be substantialy -200 mesh, and preferably at least 50%, by weight, thereof will be 325 mesh.
• the alumina and the silica may contain a very small amount of impurities like alkalies, alkaline earths and iron oxide, these apparently do not function in the same manner as the added materials incorporated in the mix according to the present invention.
• one of the materials added to the mix in accordance with the present invention is lithium fluoride or lithium carbonate
• Lithium carbonate decomposes during burning of the brick to lithium oxide, so that it will be apparent that lithium oxide itself or other lithium compound that decomposes, during burning of the brick,
• lithium fluoride is preferred.
• the lithium compound should be relatively finely divided, that is substantially all thereof should be -100 mesh, and preferably substantially all thereof is 325 mesh.
• the amount of lithium compound added to the mix should be less than 0.2%. Higher amounts markedly decrease the refractoriness under load of the resulting brick.
• the amount of lithium compound employed is from about 0.05 to about 0.15%, and preferably from about 0.05 to about 0.1%.
• the calcium hydroxide and magnesium hydroxide decompose to their respective oxides during burning of the brick so that calcium oxide and magnesium oxide, or other calcium and magnesium compounds which likewise decompose to the oxide during burning of the brick such as the respective carbonates, could serve as the equivalent of the stated calcium hydroxide and magnesium hydroxide.
• Iron oxide as Fe O is also preferably selected as the iron oxide because of its ready availability in such finely-divided form. It is also apparent that other iron compounds that decompose to Fe O during burning of the brick would be the equivalent of the iron oxide employed.
• the preferred second additive will be at least one of calcium hydroxide and magnesium hydroxide.
• the amount of the second additive added should be at least about 0.01% but should not exceed about 0.3%.
• the amount employed is not over about 0.2% and more especially not over 0.15%.
• the amount of calcium hydroxide and/or magnesium hydroxide ranges from about 0.02 to about 0.05%.
• iron oxide Fe O is employed, it is preferably in an amount from about 0.025 to about 0.05%.
• alumina plus silica and preferably from about 2 to about 3%, of a refractory plastic clay may be included to serve as a plasticizer and a green strength binder.
• a refractory plastic clay may be included to serve as a plasticizer and a green strength binder.
• examples of such clays are plastic kaolin, which is preferred, and ball clay.
• phosphoric acid may be included as enhancing cold strength, particularly when a clay is employed.
• Other binders, such as sodium lignosulfonate may be included to impart green strength and lubrication.
• phosphoric acid When phosphoric acid is employed, it may be used in the amount of from about 1 to about 4%, preferably from about 2 to about 3% (as a 75% aqueous solution of H PO based on 100 parts of alumina plus silica.
• a lignosulfonate binder When a lignosulfonate binder is employed, it may be used in an amount of from about 1
• the mix will be tempered with a small amount of water.
• Some or all of the water may be provided by binders of the type discussed above.
• the total water will range from about 2.5 to about 6%, preferably from about 3 to about 5%, by weight, based on 100 parts of the alumina plus silica.
• the materials will be mixed in accordance with conventional refractory practice, For example, a muller mixer may be employed in which case it is preferred to add the more coarse materials to the pan first, then the major portion of the moisture followed by the finer materials then the remainder of the moisture to proper consistency.
• the tempered mix is then pressed into the desired refractory brick shape.
• a pressure of at least about 4,000 p.s.i. is employed and this may range up to about 15,000 p.s.i., with a preferred pressure being from about 8,000 to about 10,000 p.s.i.
• the shaped brick is then fired to provide the ceramic bond for example, at a temperature which may range from about 1200 to about 1500 C.
• Examples v-4 In these examples a brick batch mix is prepared from: 50%, by weight, -6 mesh tabular alumina; 25% 48 mesh tabular alumina; 15% 325 mesh calcined alumina, and 10% 200 mesh ground silica. To portions of the mix are added various materials as set forth in the following table. Each mix is then tempered with an aqueous sodium lignosulfonate solution and pressed into 6 /2 x 1 /2 X 1 /2" bricks at 6000 p.s.i. The bricks are fired at 1450 C. The properties of the fired specimens are set forth in the following table:
• Each mix is then tempered amount, less than 5%, by weight, based on 100 parts with aqueous sodium lignosulfonate and pressed, at 8000 p.s.i., into brick 9 x 4 /2 x 2 /2 inches which are then fired at 1450 C. following standard refractory manufacturing practice.
• the properties of the brick are set forth in the following table.
• composition of claim 1 wherein said other compound is at least one of those selected from the group consisting of calcium hydroxide and magnesium hydroxide and is present in an amount not over about 0.2%.
• Examples 8-11 In these examples a brick batch mix is prepared from: 51%, by weight, 6 mesh fused alumina (99.5% A1 0 26% -48 mesh tabular alumina, 325 mesh calcined alumina and 8% 200 mesh ground silica, to which is added 3% plastic koalin and 3% of a 75% aqueous phosphoric acid solution. To portions of this mix are added various materials as set forth in the following table. Each mix is then tempered with 24% water, pressed into 9 x 4 /2 x 2 /2" bricks at 800 psi, and fired at 1450 C. for 5 hours using standard refractory manufacturing procedures. The properties of the brick are set forth in the following table:
• composition of claim 5 wherein said other compound is calcium hydroxide and is present in an amount not over 0.15%.
• composition of claim 5 wherein said other compound is magnesium hydroxide and is present in an amount not over 0.15%.
• composition of claim 5 wherein said lithium compound is present in an amount not over about 0.15
• composition of claim 1 wherein from about 50 to about 65% of said alumina is 6 +48 mesh; wherein from about to about 50% of said alumina is 48 Linear Deformation reheat under load Fired Apparent change, (percent)* density porosity MOR 3,10 Example Additive (ozJiufi) (percent) (p.s.i.) (percent) 1% hrs. 5 hrs.
• a refractory brick batch mix consisting essentially of from about 85 to about 95%, by weight, of 6 mesh alumina and from about 5 to about 15%, by weight, of -200 mesh silica, based on the combined weight of said alumina and said silica, the improvement comprising, in addition as added materials, between 0.05 and 0.2% of at least one lithium compound selected from the group consisting of lithium fluoride and lithium carbonate and from about 0.01 to about 0.3 %of at least one other compound selected from the group consisting of calcium hydroxide, magnesium hydroxide and iron oxide, said amounts of lithium compound and other compound being based on 100 parts of combined alumina and silica.
• composition of claim 1 wherein said lithium compound is present in an amount not over about 0.15
• composition of claim 2 wherein said lithium compound is present in an amount not over about 0.10%.
• composition of claim 1 wherein the total of said lithium compound and said other compound is not over about 0.3%.
• composition of claim 11 wherein from about 10 to about 30% of said alumina is 325 mesh.
• composition of claim 13 wherein said lithium compound and said other compound are substantially all -325 mesh.
• a brick batch mix consisting essentially of from about to about by weight, of 6 mesh alumina and from about 5 to about 15 by weight, of 200 mesh silica, based on the combined weight of said alumina and said silica, is pressed into brick form and fired, the improvement wherein said brick batch mix has as added materials, between 0.05 and 0.2% of at least one lithium compound selected from the group consisting of lithium fluoride and. lithium carbonate and from about 0.01 to about 0.3% of at least one other compound selected from the group consisting of calcium hydroxide, magnesium hydroxide, and iron oxide, said amounts of lithium compound and other compound being based on parts of combined alumina and silica.
• a brick batch mix consisting essentially of from about 85 to about 95%, by weight, of alumina and from about 5 to about 15%, by weight, of --200 mesh silica, based on the combined weight of said alumina and said silica, is pressed into brick form and fired, the improvement wherein said brick batch mix has 'as'added materials, between 0.05 and 0.2% of at least one lithium compound selected from the group consisting of lithium fluoride and lithium carbonate and from about 0.01 to'about 0.3% of at least one other compound selected from the group consisting of calcium hydroxide, magnesium hydroxide, and iron oxide, said amounts of lithium compound and other compound being based on 100parts of combined alumina and silica.
• said other compound is at least one of those selected from the group 8 consisting of calcium hydroxide and magnesium hydroxide and is present in an amount not over about 0.2%.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Compositions Of Oxide Ceramics (AREA)

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• 1968
  • 1968-07-01 US US741333A patent/US3591392A/en not_active Expired - Lifetime
• 1969
  • 1969-06-25 GB GB32199/69A patent/GB1262328A/en not_active Expired
  • 1969-06-26 SE SE09119/69*A patent/SE353894B/xx unknown
  • 1969-06-30 JP JP44051115A patent/JPS519768B1/ja active Pending
  • 1969-07-01 FR FR6922171A patent/FR2012096A1/fr not_active Withdrawn
  • 1969-07-01 DE DE19691933360 patent/DE1933360B2/de not_active Withdrawn

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